SoftBank Group is aiming to increase its stake in OpenAI by acquiring up to 1.5 billion in shares from the startup's employees, according to people familiar with the matter. The company will make a tender offer for the stock, allowing OpenAI employees to cash in shares if they choose. SoftBank contributed 500 million to OpenAI's 6.6 billion fundraising round in October, but had pushed for a larger allocation at the time, said one of the people, asking not to be named because the negotiations aren't public. SoftBank founder Masayoshi Son has vowed to step up investments in artificial intelligence as his Tokyo-based company regains its financial footing after years of missteps. OpenAI, which jumped out to early leadership in the field with its ChatGPT product, was valued at 157 billion in the last fundraising.